Heat recoverable article

ABSTRACT

Heat recoverable elastomeric materials are used to form gathers in fabrics, especially disposable garments of nonwoven fabrics.

nlted States Patent [151 3,639,917

Althouse [45] Feb. 3, 1 972 [54] HEAT RECOVERABLE ARTICLE 3,353,18911/1967 Zimmon ..2/270 X 1,102,408 7/1914 Hubner ....2/DlG. 7 [72]Inventor. Victor E. Althouse, Los Altos, Calif. 1,408,373 2/1922Lustganen "2/228 Ux [73] Assignee: Raychem Corporation, Menlo Park,Calif. 2,027,962 1/1936 Currie 3,086,242 4/1963 Cook et a1. ..264/95[22] Filed: Apr. 7, 1970 Primary Examinr-Alfred R. Guest [2]] App! 26347Attorney-Lyon & Lyon [52] US. Cl. ..2/270, 2/DIG. 7 57 BSTRACT [51] Int.Cl. ..A4ld 27/11 v [58] Field Of Search ..2/DIG. 7, 270, 125, 128, 228Heat recoverable elastomeric materials are used to f gathers in fabrics,especially disposable garments of nonwoven [56] References Citedfabrics.

UNITED STATES PATENTS 8 Claims, 4 Drawing Figures 1,544,312 6/1925 G 'ay"12/228 ux PATENTEU FEB 81972 3,6390% INVENTOR V/CTOR E. ALTHOUSE A r(JP/YE Y5 HEAT RECOVERABLE ARTICLE FIELD OF THE INVENTION This inventionrelates to fabrics, and more especially to garments and other articlesportions of which are gathered.

BACKGROUND OF THE INVENTION In recent years, increased costs oflaundering, and the deliberately introduced changes in fashions,especially women s fashions, have combined to cause or accelerate theintroduction of garments and other articles of fabrics which aredesigned to be worn or used only once or a relatively small number oftimes and then discarded. Such articles are generally referred to asdisposable garments although it will be appreciated that some of thearticles, such as sheets, are not worn. Among the many examples of sucharticles there may be mentioned party dresses and hospital and cleanroom garments.

The known reluctance of a lady to arrive at a dance or party in a dressidentical to that worn by another or, indeed, identical to the dress sheherself wore to any previous such occasion has led to the manufacture ofgarments of relatively cheap materials. Exemplary of such materials arepaper, plastic, or nonwoven fabrics which can be dyed or printed in avariety of ways. Such garments can be worn on only one occasion and thenbe economically discarded.

Hospitals are using an increasing number of disposable articles of alltypes since it is often found to be cheaper or more convenient topurchase new items then clean and where necessary sterilize them beforereuse. This applies to garments" of all types, whether for use bypatients or staff, including fitted sheets and other shaped fabricarticles.

Since an important feature of disposable garments is economic price,production costs must needs be reduced to a minimum. Thus, suchmaterials as nonwoven fabrics and paper are used as bases for thegarments, and the materials are cut and joined, such as by sewing orglueing, in the simplest manner possible. Where, however, it isnecessary that a part of the garment should fit relatively tightly butresiliently over the user, such as at a wrist or waist band, it isnecessary to incorporate elastic or similar material into the garment.This has been found to add considerably to the cost of such garmentssince the elastic has to be sewn, often by hand, into the material by atime'consuming process. Further, when such elastic is sewn into thegarment, it tends to produce tear-sensitive holes, especially inplastics or nonwoven fabrics. In those cases where sewing can betolerated, it is necessary that the elastic material be held in tensionduring sewing so that after sewing elastic recovery will cause thefabric to gather. That necessity naturally complicates the sewing step.

It has also been found that hospital patients become depressed if theyhave to wear ill-fitting, shapeless garments, so that gathers whichimprove the fit would be desirable if they could be economicallyincorporated.

SUMMARY OF THE INVENTION According to this invention, there is providedan economic process for gathering a fabric which comprises attaching aheat recoverable material which is elastomeric in its heat stable formto a portion of the fabric and heating the material to cause it torecover and gather the fabric. There is also provided by this inventiona gathered fabric comprising a heat recovered elastomeric material. Oneobject of the present invention is to provide a new and economic meansand method of gathering fabrics.

A further object of the invention is to provide disposable garmentshaving elastic portions capable of accommodating a variety of sizes.

These and other objects and advantages of the invention will be apparentfrom the detailed description of the invention and the accompanyingdrawing, in which:

FIG. 1 is a side view, partly in section, of a garment sleeve having anattached band of heat shrinkable elastomeric material.

FIG. 2 is a view of the sleeve shown in FIG. 1 after recovery of thematerial.

FIG. 3 is a pictorial view of a hospital gown whose cuffs have beengathered according to the invention.

FIG. 4 is a perspective view of a hospital gown whose sleeves have notbeen gathered by the invention.

DESCRIPTION OF THE INVENTION As used in the present specification anelastomeric material is a substance that can be stretched at roomtemperature to at least about twice its length and which after removalof the stretching load will immediately return to approximately itsoriginal length.

It is not necessary that the material be elastomeric when in its heatshrinkable form, i.e., prior to heat recovery, although in practice itmay be. To give a gather that has give" it is only required that thematerial be elastomeric after recovery.

The material may be rendered heat recoverable by any of the methodsknown for imparting this property. In general, the material may beformed into an article having an original configuration, then deformedat an elevated temperature, and subsequently cooled while maintainingthe deforming force. Such an article will retain its new configurationuntil it is again heated to an elevated temperature. Upon heating to thetemperature of recovery, the material recovers to its previously held,heat stable configuration. Methods of achieving these results aredisclosed, for example, in US. Pat. No. 2,027,962 to L. M. Currie and inUS. Pat. No. 3,086,242 to P. M. Cook et al., the disclosures of whichare incorporated herein by reference.

The heat recoverable material can be applied to the fabric by anyconventional means, for example by using contact cements,pressure-sensitive adhesives, and heat sealing provided of course thatthe temperature required for heat sealing is lower than that of therecovery, or provided that recovery is prevented during the application.It is however within the scope of the invention to apply and recover inone step so long as the adhesion between the fabric and the material issufficiently strong immediately after application to enable the materialto carry the fabric with it during recovery. Where sewing can beemployed, the recoverable material can be sewn to the fabric withoutneed for the simultaneous application of tension necessary withconventional elastic elements used in garment manufacture. Of course,the particular preferred method will depend both on the material and thenature of the fabric to which it is being applied.

The shape of the heat recoverable material varies with the particularapplication. For example, if a sleeve of a garment is to have an elasticwristband, then a piece of recoverable material may be applied to theinside or the outside of the sleeve. The piece may be a strip or anendless band. If, for example, a garment is simply to be shaped bygathering a small portion of the fabric, a shrinkable strip may beapplied to an appropriate portion of the garment. A band may be made byexpanding tubing, for example, as described in the abovementioned US.Patents, and cutting off suitably sized lengths of the expanded tubing.A strip may be formed from, for example, tubing or sheet. Those skilledin the art will appreciate that a variety of effects may be achievedusing recoverable material of different shapes. Further, the degree ofrecovery may be made to differ from one part of the material to another,so that different extents of gathering may be achieved when the materialis recovered.

The material may be covered, either by the fabric itself or by othercovering materials, to enhance the appearance of the garment. Forexample, the band to tighten a wristband may be applied to the inside ofthe sleeve a short distance from the end of the sleeve, and part of theend region turned in to form a hem containing the recoverable band.

The material may be caused to recover by many of the commonly usedmethods for recovery of such materials, such as by use ofa hot-air gun,an iron, or an oven.

In general, materials suitable for use in the invention are thosecontaining elastomeric regions and nonelastomeric regions. It isbelieved that, below a transition temperature of the nonelastomericregions, the elastomeric regions can be held in a deformed state (suchas that achieved by imparting heat recoverability to the material) bythe nonelastomeric regions while still allowing the gross material todisplay elastomeric properties. Above the transition temperature, e.g.,a glass transition or crystalline melting point, the nonelastomericregions have insufficient strength to maintain the deformation.

As elastomeric materials suitable for use in this invention, there canbe mentioned by way of example those described in US Pat. No. 3,265,765to Holden et al., the disclosure of which is incorporated by referenceherein. Briefly, these materials are elastomeric block copolymers of theformula A-BA wherein each A is an independently selected nonelastomericpolymer block and B is an elastomeric polymer block. Preferably eachterminal A block is formed from the same monomer or monomers.Advantageously, each end block A has an average molecular weight of2,000 to 100,000 (preferably 5,00050,000) and has a glass transitionabove about 25 C. (preferably above 50 C. while the center block B hasan average molecular weight of 25,000 to 1,000,000 (preferably 50,000 to500,000) and a glass transition temperature below 10 C. (preferablybelow C. and more preferably below 25 C.). Advantageously the differencein glass transition temperatures of the end and center blocks is atleast 40 C., and preferably above 100 C. The end blocks togetheradvantageously constitute to 50 percent (preferably to 40 percent) byweight of the polymer.

Preferred for block B are polymers of aliphatic conjugated dienes, e.g.,isoprene, methyl isoprene, butadiene homopolymers and styrene/butadieneand butadiene/acrylonitrile copolymers.

Preferred for blocks A are polymers of styrene'type monomers, e.g.,styrene itself, methyl styrene and chlorostyrene.

A preferred copolymer is one in which B represents an elastomericpolyisoprene block while each A represents a polystyrene block.

Also suitable are materials disclosed in US. Pat. application No.65,953, filed Oct. 31, 1960, by P. M. Cook (British Patent SpecificationNo. 1,010,064), crystalline neoprene rubbers like those manufactured byE. l. du Pont de Nemours and Co., Inc., under the designation NeopreneHC, and high-ethylene content crystalline ethylene-propylene copolymerelastomers, e.g., Vistalon 3708, available from Enjay Corporation.

For use in the present invention, the polymers are preferablycross-linked by conventional techniques, e.g., by ir radiation or bychemical cross-linking agents, prior to impartation of heatrecoverability.

Of course, the polymers can contain any of the usual additives, e.g.,fillers, antioxidants, flame retardants, pigments, so long as suchadditives do not unduly interfere with the elastomeric properties of thematerial.

With reference now to the drawings, FIGS. 3 and 4 depict hospital gownsgenerally indicated at l. The gowns are preferably of the disposablevariety and manufactured from nonwoven fabric. For reasons of economy,the sleeves 2 of the gowns are not shaped in any way and hence do nottaper toward the wrists. Instead, such gowns have large diameter cuffs,as shown at 3. Those cuffs constitute a danger, as they may dragsurgical instrument trays, tables, and other surfaces. Referring now toFIG. 1, there is shown a sleeve 2 ofa gown of the type illustrated inFIG. 4 to the inside of the cuff 3 of which has been attached a band 4of heat shrinkable elastomeric material. FIG. 2 shows the same sleeveafter recovery of the band 4 by heating, while FIG. 3 shows at 5 theeffect on the gown 1. In similar fashion, the head band of the cap,waist, and cuffs (particularly for clean room use) of such garments canbe gathered by the application of this invention.

The invention is further illustrated by the following examplesofcurrently preferred embodiments.

EXAMPLE 1 A styrene/butadiene block copolymer sample (Kraton 3125,available from the Shell Oil Co.) is formed into a slab. The slab was 3inches X 5 inches 0.020 inches. It was then irradiated in a 1 MeV beamto a dose of 15 Mrad and expanded at 1 10 C. so that the 5-inch lengthbecame 15 inches, i.e., an expansion of 3X, and cooled while maintainingit expanded. The slab was cut in the expansion direction into strips0.25 inches wide. Using a contact cement (Roberts' Anchor Weld 0308) onestrip was bonded to each cuff ofa nonwoven fabric (du Pont Tyvek)disposable garment. The sleeve section was then heated to C., when thestrip recovered to its original length and gathered the cuff. The cuffwas found to be elastically deformable, i.e., it could be readilystretched to allow a hand to pass through it and thereafter form a snugfit around the wrist. The properties of Kraton 3 are described in ShellChemical Company Technical Bulletin SCR 68-193.

Example 2 A strip of Thermofit SFR tubing, 2 inches long, 025 inchesdiameter and 0.020 inch wall thickness was irradiated to a dose of 20Mrad in a 1 MeV beam. Thermofit is a trademark of Raychem Corporation.The material is a blend of a silicone rubber with a thermoplasticmaterial, the blend being elastomeric and capable of having heatrecoverability imparted to it. The tubing was heated to C. in an oven,stretched to 4 inch in length, and cooled to room temperature, whilemaintaining that length. It was then attached, with General ElectricSilicone Contact Cement 516 to Kimlon, a cellulosic nonwoven fabricmanufactured by Kimberly-Clark Corporation. Reheating to 150 C. causedthe tubing to shrink, resulting in a gathered material which waselastically stretchable.

Example 3 A strip of Neoprene HC, 6 inch X 0.25 inch X 0.020 inch wasirradiated as described in example 2 and similarly stretched to 12inches at 75 C. The cooled, elongated strip was attached to Kimlon witha contact cement (Roberts Anchor-Weld 0308). Reheating to 75 C. resultedin an elastic-gathered fabric article.

Example 4 Example 3 was repeated, with the change that Vistalon 3708, anethylene-propylene elastomer manufactured by Enjay Corporation (StandardOil of New Jersey) was expanded at 100 C. The adhesive used was GeneralElectric Silicone Contact Cement 576. Reheating the assembly to 100 C.produced an elastic-gathered article.

lclaim:

1. A shaped element gathered in at least one region at tached to a heatshrunk material selected from the group of materials which areelastomeric following heat recovery from a dimensionally heat unstablestate to a dimensionally heat stable state.

2. An article according to claim 1 wherein said material is anelastomeric block copolymer having the general formula A-B-A in whicheach A is an independently selected nonelastic polymer block and B is anelastomeric polymer block.

3. A shaped fabric article gathered in at least one region attached to aheat shrunk material selected from the group of materials which areelastomeric following heat recovery from a dimensionally heat unstablestate to a dimensionally heat stable state.

4. An article according to claim 3 wherein said material is anelastomeric block copolymer having the general formula AB-A in whicheach A is an independently selected nonelastomeric polymer block and Bis an elastomeric polymer block.

5. A garment attached in at least one region to a heat shrinkablematerial, which material is selected from the group of materials whichare elastomeric following heat recovery from a dimensionally heatunstable state to a dimensionally heat stable state.

8. An article according to claim 7 wherein said material is anelastomeric block copolymer having the general formula A-B-A in whicheach A is an independently selected nonelastomeric polymer block and Bis an elastomeric polymer block.

1. A shaped garment gathered in at least one region attached to a heatshrunk material selected from the group of materials which areelastomeric following heat recovery from a dimensionally heat unstablestate to a dimensionally heat stable state.
 2. An article according toclaim 1 wherein said material is an elastomeric block copolymer havingthe general formula A-B-A in which each A is an independently selectednonelstomeric polymer block and B is an elastomeric polymer block.
 3. Ashaped fabric article gathered in at least one region attached to a heatshrunk material selected from the group of materials which areelastomeric following heat recovery from a dimensionally heat unstablestate to a dimensionally heat stable state.
 4. An article according toclaim 3 wherein said material is an elastomeric block copolymer havingthe general formula A-B-A in which each A is an independently selectednonelastomeric polymer block and B is an elastomeric polymer block.
 5. Agarment attached in at least one region to a heat shrinkable material,which material is selected from the group of materials which areelastomeric following heat recovery from a dimensionally heat unstablestate to a dimensionally heat stable state.
 6. An article according toclaim 5 wherein said material is an elastomeric block copolymer havingthe general formula A-B-A in which each A is an independently selectednonelastomeric polymer block and B is an elastomeric polymer block.
 7. Afabric article attached in at least one region to a heat shrinkablematerial, which material is selected from the group of materials whichare elastomeric following heat recovery from a dimensionally heatunstable state to a dimensionally heat stable state.
 8. An articleaccording to claim 7 wherein said material is an elastomeric blockcopolymer having the general formula A-B-A in which each A is anindependently selected nonelastomeric polymer block and B is anelastomeric polymer block.